I bought a new cylinder head from a 220 sedan. I cleaned it up to better examine the condition. I don't know much about heads, so I thought I'd post pictures with a few questions here.
The first two pics just show the top and bottom of the head. The top looked to be in pretty good shape. I had a question about the bottom, though. There is some surface roughness around the back cylinders that I wondered about. See pics 3 and 4. A bit of roughness inside the combustion chamber didn't seem like a big deal to me, but this is on the gasket surface. Should I worry about that?
Also, in pic 5 there a pit between two of the cylinders that seems to be a bit eroded. Is that a problem? Should I fill it and mill it flat or not worry about it?
In pic 4 top center is a cooling passage (I think). It seems to have an insert or something in it that sticks out very slightly above the surface of the head. Anyone know anything about that?
I don't think you're going to like what I have to say so take it with as many grains of salt as you need.
Don't expect any miraculous increase in performance with the HC head install. There is some but I was woefully disappointed in it. Search the board for “High compression head” and you’ll get some really good info. For example this thread, http://www.benzworld.org/forums/unim...mpression+head.
Now about your head. I wouldn’t install a head with out going through it first.
Check the guides for wear, replace as necessary. Grind the seats and valves. Deck the surface to remove some of those imperfections and make sure it’s true.
Check all of the valve adjusting bolts for proper tightness and replace as necessary. Install new seals, check the cam for wear and end play and check the cam bearings for wear. Check all of the arms for wear. I would replace all of the springs as a matter of routine.
I think I spent about $300 - $400 at the machine shop to have the head I bought tuned up. Plus probably another $300 for parts. Numbers in ( ) are MB part numbers for reference.
valve springs, inner = (A180 053 06 22)
valve springs, outer = (A 180 053 06 20)
exhaust valve spring retainers= (A 180 050 22 23)
inlet valve stem seal holders = (A 127 053 00 58)
rocker arm spring = (A 180 993 12 25)
rocker arm spring annular = (A 180 993 09 25)
inlet valve guides = (A 180 050 05 24)
exhaust valve guides = (A 121 050 21 24)
timing chain tensioner = (A 130 050 03 11)
valve adjustment stud = (A 180 055 07 74)
and probably some other smalls.
If you need valves forget about it. The exhaust valves are sodium filled and very expensive.
Add another $150? For the gasket set, which does not include the valve cover gasket. New plugs, $35 I used NKG BP6HS.
IMHO, don’t bother with the head swap unless there is something wrong with your current motor. If you really want to swap the head over use the one you have for a core and buy one all ready to bolt in and warranted, I wish I had.
The good news is The motor purred like a kitten after the swap and it runs great.
Regards,
Jeff
I would put an M130 into your truck before even bothering with a high compression head. I tried the HC head with dual carbs, and I didn't really notice much difference. Now, an M130 - huge difference.
I'm not looking for a big boost in power. I'd rather see a little better fuel economy more than anything. The theoretical increase in efficiency as compression ratio increases is well documented. How that will pan out in this case remains to be seen. I've never heard of anyone else doing this kind of stuff (on a 404) for increased fuel economy. It's fun to try new stuff.
It sounds like you're not worried about the surface roughness. I'll get the surface decked. How about that hole between the cylinders? I don't know what the purpose of that passage is, but it's pretty eroded in a couple of places. Should I worry about that?
I needed to replace the head gasket anyway, and posted a topic about a thinner head gasket to increase compression. The advice was that I might as well replace the head since it was no more work.
That parts list is great Dog Taxi. Thanks. These are the parts I need for the sedan head? I was hoping to reused many of the parts off my original head. I was worried that the valves are not the same, but have not checked yet. Are they? Thanks.
You're not going to realize any noticeable boost in fuel economy by putting a higher compression head on this particular engine. Maybe you'll get 8.5 mpg instead of 8.
Here's a question I don't have the answer to but maybe you can ponder it: if the piston only draws in N volume of air/fuel mixture, then compresses it to stociometric ratio for combustion, how does reducing the overall volume of the cylinder (by installing the high compression head) give you more power? It seems to me that with an HC head, you'd get less volume of air/fuel mixture with the HC head. You'd need something else like a different crank or timing to give you more "bang" for the same amount of inducted volume, which would give you your desired volumetric efficiency.
The only option I can think of to truly get your VE higher (and a noticeable increase in power) is by forced induction on this engine...?
That's the conclusion I came to when fiddling with the HC heads on the m180, anyway. It's also why I suggest finding an M130, since the 2.8 litre motor makes a huge difference in power when driven in a 404. (like easily a gear higher everywhere driving on hills)
That hole between the cylinders is I think a coolant channel. You should fix that before proceeding. Have you dye checked the head for cracks yet? That head seems pretty worn, just looking at the amount of pitting on it.
It's been a while since I re-did a head for a 404, but I seem to remember that the valves were different size. (I might be totally wrong) You should install new valve guides and seats. Any sticky rocker adjusters need to be renewed. Make sure you don't have the hollow cam, they're an older design I believe.
You can use the same cam from the other head. I've tried the LC vs. HC cam and from what I can tell the timing is the same. I tried swapping the cams around to see if there was any difference and I could not find any.
There is very, very little room between the head and valve edges on the m180, and you can't plane very much off the head, especially if you think you're going to get more compression by planing more material off.
Speaking of planing, when these heads come off the motor they often will flex fore to aft, and become bowed. If you then machine the head flat again, the cam bore will not be straight. There are two ways to resolve the problem, one is to kiln the head and get the metal to relax flat again by itself, or to use shims on the end towers to get your cam bore straight again. If you don't check and/or solve this, you'll get excessive wear on the cam towers and soon oil pressure loss from the wear.
Last edited by aaronsb : 06-20-2008 at 06:43 PM.
Reason: valve edges, not tips!
Those part numbers were for parts for the HC head. I believe they are interchangeable though, including the valves.
I must say, you could buy a lot of fuel with the monies you are going to spend on the head swap. I don’t know if I get better mileage now or not. I have never measured the mpg of my 404 but I doubt it is worth the trouble and expense to swap the head in hopes of saving a few pennies on fuel.
aaronsb
The volume of air/fuel mixture drawn into the cylinder is equal to the volume displaced by the piston in its travel. It is independent of the total volume of the cylinder/head combustion chamber; you get the same amount of fuel/air mixture drawn into the cylinder with either head. By increasing the compression ratio you get a more powerful explosion from the fuel mixture.
Horsepower comes from torque. Torque is a result of the combustion process forcing the piston downward and rotating the crank. This output is measured as Torque. The idea is to generate high enough pressure on each stroke often enough to generate the necessary Horsepower.
The relationship between compression ratio and HP is not linear. It seems the best results are achieved when boosting the compression ratio between 7.0:1 and 9.0:1 which is fortunate for us seeing as that the range for the 180 head swap. A rough estimate is 4% increase in Hp for each 1 increase in the compression ratio. If the 180 has 82HP at 7.0:1 then it should realize about 88HP at 8.9:1.
I am not sure what you mean by Stociometric ratio. Did you mean Stoichiometric ratio?
Regards,
Jeff
But seriously folks... I'd be happy with a couple more miles per gallon. Very happy really. The best I've ever measured is 10 mpg. If I got it up to 12 I'd count that as huge.
Your point about the money is quite right. Considering how little I drive it I will probably never see a return on money invested. The fact is that it bothers me that it gets really crappy fuel economy and I want to see if I can do anything about it. It's a "can I do it" kind of thing. I find that the technical challenge is the reason I start many projects like this.
Of course I'm still a cheap bastard and will try and do it for as little as possible. I very much hope you're right about the valves being the same. I plan to use as many parts as possible from the old head.
Great pic of the low and high compression heads together. How much did you mill off your HC head? I ask because the recessed areas look much smaller than on mine.
I plan to mill off as little as possible. I'll check the service manual for the minimum head height. I assume that the min height has to do with chain tension and that whole pesky valve vs. piston collision thing.
Just bought the head as shown. It had three exhaust valves in it, along with the valve guides and whatever you call the steel thingy that the springs sit on.
I got the valves out today. Was a bit of trouble. Didn't realize that the head has two springs per valve. Damn Germans! Modified a regular valve spring compressor for that; no way I was paying $200 for the Mercedes tool.
Figured the valves would be junk, but they seem in really good condition. They have a bit of scale on them, but that easily comes off. Is that lead deposit? The part number on all the valves is:
A 1800531105 P
SP 60 KSN 2577
That part number (minus the A and P) matches Scott's off EI, so I guess the sedan and 404 used the same valves. That's good. They guy I bought the head from had a bunch on the shelf, one with the whole valve train attached. It even had the plugs, wires and distributor cap! He said I could have the valves and everything else if I wanted, no charge. That head looked a bit more banged up than mine so I doubt the valves look as good, but with all the grease and carbon it's hard to be sure.
My engine only had 5600 Km when I bought it (~11,000 now) so I gotta think my valve train is still pretty good.
Also checked the flatness of the head. Put it on a granite block. If memory serves that's flat to 0.0002". The head looked completely flat on the block.
Modified a regular valve spring compressor for that; no way I was paying $200 for the Mercedes tool.
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